There are two major uses for decolored wax encompassing candle manufacture and paper coatings. In addition, other utility for these waxes concern preservative coatings obtained by dipping or emulsion of the item to be preserved in a wax stream. In order to have a salable commercial product the particular wax must meet certain color specificities. The paraffinic wax is tested against Saybolt Color Test ASTM D-156. The waxes are usually derived from distillate as colored distillate wax. The ultimate Saybolt color value can only be measured against the contemplated end-use of the product. The microcrystalline wax is usually of a darker color, even in the finished product, which is measured by ASTM Color Test D-1500. Here, a value of less than 2.0 is usually considered synonymous with a high grade wax.
The basic concept of removing color forming impurities from these types of wax streams has been practiced in the field for many years. Currently, the wax is sometimes process-finished by percolation through a bed of bauxite clay. The latter is derived usually by rudimentary mining techniques to acquire bauxite mineral ore which will contain mostly hydrated impure aluminum oxide with ancillary quantities of silica, titania, kaolinite and hematite. Greater than 50% of the pore size of bauxite are larger than 350 A. No more than 60% of the pores are of a size less than 350 A. While not wishing to be bound by any theory in regard to this invention, applicants have now discovered a criticality in the pore size distribution of the adsorbents. One adsorbent which has been determined to greatly outperform other conventional adsorbents has less than 10% of the pores of a size of greater than 350 A. This criticality is very important because regeneration conditions can be carefully chosen to mitigate change in the pore size distribution and thereby preserve the life and quality of the adsorbent.
It was surprising and totally unexpected, and, as shown in FIG. 3 herein completely unpredictable that by using refined aluminum oxide having at least 60% and preferably more than 90% of the pore size less than 350 A as an absorbent, in contradistinction to bauxite, that the static bed adsorbent system becomes as much as 200 percent more efficient. And implementation of the instant refined aluminum oxide with prescribed pore size distribution will result in lower maintenance cost, lower operation cost and a mitigation of environmental hazards, at least as they relate to the regeneration aspects of the adsorbent bed.
Two U.S. patents issued in the late 1930's, Breth et al U.S. Pat. Nos. 2,121,518 and 2,170,628 disclose a process for removal of discoloring agents from petrolatum, including waxes, by the use of a bauxite adsorbent. Prior to use of the bauxite, heating is undertaken at 600.degree. to 1600.degree. F. After exhaustion of the bauxite it is regenerated by a similar high temperature heat treatment. It has been determined that whatever pore structure the bauxite would possess having pores less than 350 .ANG. would probably be destroyed in this preheat or regeneration step of the patentees. In Hess et al, U.S Pat. No. 3,258,417, a process is described for dewaxing by contact with a molecular sieve adsorbent. The principal object of the patentee's disclosure is to provide an improved method for the removal of wax from oils, natural or synthetic.
A decoloring process for waxes is described in Dole U.S. Pat. No. 2,554,244 comprising subjecting a crude wax to treatment with bauxite at high and low temperatures. The multi-temperature level processing produces a highly refined, highly stable, low melting point wax. Decolorization of hydrocarbon oils is performed in the presence of uncalcined, non-activated alumina according to the disclosure of U.S. Pat. No. 2,926,135, Engel et al. It is preferred that the starting adsorbent is used in a particle size of 0.25 to 5 mm and is impregnated with a quantity of an aqueous solution of an aluminum salt which is sufficient to fill the pores of the alumina particles. In processes where bauxite is used in the filtration of waxes, a regeneration scheme, as exemplified by Robertson et al, U.S. Pat. No. 2,496,942 is usually employed to renovate the bauxite at heating conditions of between 600.degree. and 1600.degree. F. This severe renovation technique can destroy most of the small Angstrom-sized pores and acts to depreciate the quality of the absorbent in decolorizing a wax. Finally, U.S. Pat. No. 4,301,037, Sanchez et al, discloses an extruded alumina catalyst support having controlled distribution of pore sizes. As shown in FIG. 1 of the patent, over 70% of the pore sizes are micropores with specific distribution of the macro and intermediate pores of the sieve. There is no disclosure of use of any type of micropore refractory oxide sieve for wax decolorization.